* exception is the only correct way to notify an error in constructor
* exceptions are for error handling
	* exceptions are not for exiting from loops
	* exceptions are not for passing values
* exceptions are to restore after error and continue processing
	* skip not critical action:
		* display phone numbers example
		* display organizations in building example
	* fallback:
		* memory-consuming algorithm example
		* search failed example (null screen)
		* open document in MsWord (err msg)
	* fail on critical action:
		* memory allocation on game start
		* incorrect command in text interpretator
* exceptions are the part of a contract
* global try-catch
	* show example (cannot restore, but fails gracefully)
* std hierarchy
  https://ru.cppreference.com/w/cpp/error/exception
